Final answer:
Telomeres protect chromosomes from losing genetic information during cell division by means of extensions added by the enzyme telomerase. This enzyme elongates the telomeres by adding specific DNA sequences, ensuring the stability of the genome.
Step-by-step explanation:
Telomeres function to protect chromosomes by preventing the loss of genetic information during cell division. Each time a cell divides, it must replicate its DNA, and due to the nature of DNA replication, the very ends of chromosomes are not fully copied. Without telomeres, important DNA sequences could be left unprotected and lost, potentially leading to malfunction of the cell. Telomeres are extended by the enzyme telomerase, which adds repetitive DNA sequences to the ends of chromosomes, thus maintaining their length and integrity over time.
In humans, the sequence TTAGGG is repeated between 100 to 1000 times in the telomere regions. The discovery of telomerase was a significant breakthrough in understanding how the ends of chromosomes are preserved. This enzyme, for which Elizabeth Blackburn, Carol W. Greider, and Jack W. Szostak received the Nobel Prize in 2009, attaches to the end of the chromosome and elongates it by adding nucleotides that are complementary to an RNA template that is part of the enzyme itself. This process occurs in germ cells and adult stem cells, but not in most adult somatic cells, and is linked to cell aging and overall chromosome stability.